Just in-case it is a mistake I am making, can you please confirm whether I should install the driver first and then insert the USB GPS dongle, or insert the dongle and then let Windows search for the driver?

You need to install the driver first. The link that you provided should have the latest driver for the unit. Just save the file directly to your desktop and extract it. Double-click on the Prolific Driver Installer application and let it install the driver.

In the ND-100S application, have you tried pressing the Cold Start button? You can do this by going to Tools > Cold Start GPS. This will reset your GPS Receiver. Please make sure to attach the cable to the device as to extend the unit away from the computer. The reason for this is that some notebooks, laptops, and tablets produce a high level of electrical interference. In turn, it weakens the GPS signal within close proximity of the device.

Now, let the program run for a few minutes or so outside with a clear access to an open sky.